The present invention is in the field of olefin oligomerization. More specifically, the present invention relates to oligomerization of olefins with an activated catalyst.
Oligomers of lower alkenes (ethene, propene, the butenes and the pentenes) are commercially useful as, for example, relatively high-octane components of motor fuels, and as intermediates in the production of surfactants.
The use of nickel sulfate associated with a porous, inorganic oxide such as alumina for catalyst purposes in olefin oligomerization has been suggested. See, for example, U.S. Pat. No. 2,794,842, which describes the use of nickel sulfate supported on silica, alumina, silica-alumina and kieselguhr. This patent states that a nickel sulfate catalyst should be activated by heating in an oxygen-containing atmosphere at a temperature of 800.degree.-1100.degree. F.
U.S. Pat. No. 3,959,400 describes the dimerization of C.sub.2 to C.sub.4 light olefins using a nickel sulfate catalyst which has been activated by calcination at a temperature of 750.degree.-1150.degree. F. in an inert, oxygen-free, nonreducing atmosphere. This patent describes the regeneration of a nickel sulfate catalyst by (a) purging overnight at 550.degree. F. with helium, (b) replacing helium with air at 50 cc/minute/cc of catalyst, (c) heating rapidly in air to 950.degree. F., (d) holding for 20 minutes at 950.degree. F., and (e) replacing air with helium for 2 hours at 950.degree. F.
U.S. Pat. No. 3,442,964 describes the dimerization of olefins using nickel sulfate associated with a synthetic cracking catalyst such as silica-alumina. This patent teaches that the dimerization catalyst is activated initially by heating in "inert gas", nitrogen or air to temperatures in the range of 350.degree.-850.degree. C., with the use of air being preferred for activation. It describes the activation of a catalyst consisting of nickel nitrate on silica-alumina by heating in air at 550.degree. C. after which the air is replaced with nitrogen and the catalyst is cooled to dimerization reaction temperature.